Fitting with torsion box, of plastic material reinforced with carbon fibre, for coupling a drive motor / spindle unit for trimming of a horizontal stabiliser of an aircraft

ABSTRACT

Fitting with torsion box produced from a plastic material reinforced with carbon fiber, comprising a torsion box ( 2 ) with side walls and individual members for attaching the box to respective frames of the tail fuselage ( 1 ), along with a stiffening element ( 4 ) which joins the side walls ( 2   a,    2   b ) and which comprises individual end parts ( 4   a,    4   b ) and a central part ( 4   c ); 
     where 
     
         
         each end part ( 4   a,    4   b ) comprises first sections ( 4   d,    4   e ) which are extended parallel to the side walls ( 2   a,    2   b ) to both sides of the central part ( 4   c ), second sections ( 4   f,    4   g ) which are extended towards the corresponding side wall ( 2   a,    2   b ) and third sections ( 4   h,    4   i ) each one backing onto and attached to the side wall ( 2   a,    2   b ); 
         the first sections ( 4   e,    4   d ) of the end parts ( 4   a,    4   b ) and the side walls ( 2   a,    2   b ) of the torsion box include individual primary passage holes ( 5   a,    5   b,    5   c,    5   d ) aligned in order to create the first fastening.

TECHNICAL FIELD OF THE INVENTION

This invention belongs to the technical field of aeronauticalconstructions, particularly to the sector of trimmable horizontalstabilizers of an aircraft, and more particularly to the fittings forthe spindle used to vary the height of the fastening point of thehorizontal stabilizer and thus permit trimming of the stabilizer.

STATE OF THE PRIOR ART OF THE INVENTION

The fastening of a trimmable horizontal stabilizer in an aircraft isusually carried out by means of coupling the stabilizer to one or twopivoting points and a fastening point. So that the plane of thehorizontal stabilizer can trim the one or two fastening points it has tochange its position vertically in order to permit the stabilizer topivot on the pivot point or points. In order to allow this change ofposition, a motor/spindle is usually provided secured by a fitting. Therotation of the spindle in one direction or the other causes thefastening point to rise or fall. The fitting which secures that spindleis a metallic fitting which can be secured by a torsion box which is inturn secured by one or two master frames. The motor driving the spindleis anchored in the fitting while the spindle, which is connected to themotor via a swivel device, pivots with respect to the fitting in such away that the sum of moments at the fastening point is zero and the loadis virtually a pure vertical load. Typically, the metallic fittingusually presents a primary fastening and a secondary fastening in orderto be able to comply with “fail-safe” requirements in such a way that ifone of the fastenings fails, the other supports with the load withoutendangering the integrity of the aircraft. The primary fasteningtherefore has to resist the ultimate load while the secondary fasteningonly needs to withstand the limit load. The primary fastening is usuallyduplicated and has female lugs while the secondary fastening has male orfemale lugs.

In spite of trends in recent years to introduce the use of compositessuch as CFRP (Carbon Fibre Reinforced Plastic) in as many components ofan aircraft as possible owing to the saving in weight implied by thismaterial compared to aluminum, the majority of aircraft manufacturersare reluctant to use carbon fibre for manufacturing fittings on accountof the complexity which they display, which makes their manufacturefairly expensive. This complexity is particularly pronounced in the caseof the fitting for the motor/spindle unit due to the relatively largenumber of lugs which it has to have and the arrangement of them.

It was therefore desirable to have a fitting for a motor/spindle unitfor trimming of a horizontal stabiliser of an aircraft that wouldovercome those drawbacks and which, therefore, could be manufactured ina composite such as CFRP, simply and economically.

DESCRIPTION OF THE INVENTION

The aim of the present invention is to overcome the difficulties of thefittings of the state of the art by means of a fitting for coupling amotor/spindle unit for trimming of a horizontal stabilizer of anaircraft which comprises a duplicated primary fastening for the couplingof a pivoting motor/spindle unit, and a secondary fastening, whosefitting comprises a torsion box with a first side wall and first meansof attachment for attaching the first side wall to a first frame of thetail fuselage of the aircraft, and with a second side wall and secondmeans of attachment for attaching the second side wall to a second frameof the tail fuselage. According to the invention, the side walls of thetorsion box are attached together by means of a stiffening elementarranged between said side walls. This stiffening element comprises afirst end part attached to the first side wall, a second end partattached to the second side wall, and a central part which joins the endparts. Each end part comprises individual first sections which areextended parallel to the side walls to both sides of said central part,individual second sections which are respectively extended from one ofthe first sections to the corresponding side wall, and individual thirdsections each one backing onto and attached to the side wall, thuscreating individual end parts with a transverse section in the form ofan omega. The first sections of the first end part of the stiffeningelement and the first sections of the second end part of the stiffeningelement include individual first primary passage holes, while the sidewalls of the torsion box include individual second primary passage holesaligned with the primary passage holes in order to create the primaryfastening. In turn, the second fastening consists of at least onesecondary passage hole in the central part of the stiffening element.According to the invention, said sections of each end part of thestiffening element can comprise an additional laminated layer preferablymade of the same material as the rest of the stiffener, in such a waythat this laminated layer has a transverse section complementary to thatof the sections creating the end part, in other words, that it also hasthe said omega configuration. The laminated layer can be formed by meansof an additional stacking on top of the sections of the end parts of thestiffening element, in such a way that, although the laminated layerforms an additional part of the stiffening element, it creates a singlepiece with the latter.

In an embodiment of the invention, the first primary passage holes arearranged in individual reinforced zones of the first sections of the endparts of the stiffening element, and preferably in individual firstprimary lugs emerging from the respective edges of the first sections ofthe end parts of the stiffening element, while the second primarypassage holes can be arranged in individual reinforced zones of the sidewalls of the torsion box, these reinforced zones being for examplethickened zones or ones provided with a hybrid titanium-CFRP laminate,and preferably in individual second primary lugs emerging from therespective edges of the side walls of the torsion box. In turn, eachsecondary passage hole can be arranged in a reinforced zone of thecentral part of the stiffening element. When the end parts of thestiffening element include the said additional laminated layer, thefirst primary lugs emerge from the laminated layer in the respectiveedges of the first sections of the end parts of the stiffening element.

The third sections of the stiffening element can be attached to therespective side wall of the torsion box by means of gluing, or riveting,though the stiffening element and the torsion box can also be a monoblocpiece.

The structure described above allows the torsion box and the stiffeningelement to be able to be shaped starting from a plastic materialreinforced with carbon fiber, as well as permitting an optimumdistribution of the loads acting on the fitting and the torsion box. So,the loads applied to the fitting are essentially loads in the verticaldirection, though it can also be subjected to small longitudinal loadsowing to the balancing of the horizontal stabilizer. The lateral load isvirtually zero, which avoids problems of the third sections of the endparts of the stiffening element from becoming detached, which issomething that could occur. These vertical loads on the primaryfastening are applied in the primary passage holes, for example in thelugs located in the stiffening element, and in the side walls of thetorsion box. These loads are transmitted to the walls of the torsion boxand are then converted into shear flows in the cores of the closingframes.

The load applied to the first primary passage holes which are preferablylocated in the lugs is transmitted to the wall of the torsion box viaattachments provided in the respective third sections of the end partsof the stiffening element. These attachments are preferably rivetedattachments since the failure load of such riveted attachments can beknown more accurately than when using glued pieces. These rivetedattachment also have the advantage that the vertical loads of thesecondary fastening are transferred to the walls of the torsion box viathese riveted attachments without the flow of loads being transferred atany moment via glued attachments. Finally, loads in the longitudinaldirection are transmitted to the walls of the torsion box without anykind of eccentricity via the passage holes, preferably located in thesaid lugs, situated in the walls of the torsion box.

In order to manufacture the fitting with torsion box of the presentinvention, techniques can be used that are conventional in themselves,which permit the pieces to be shaped and, which, if it is planned tocarry out the attachment by riveting, permit them to be rivetedtogether. So, the pieces can be obtained by means of processes in which,in the case of pieces manufactured separately and then riveted togetherso that the loads are transmitted via the riveted attachments, thepieces are manufactured in pre-peg with ATL and hot-formed, or in thecase of pieces that are entirely integral they can be manufactured forexample by means of Resin Transfer Molding® with attachments via theinterfaces which only contain resin.

It can be seen that the fitting with torsion box of the presentinvention is easy and cheap to manufacture and is less heavy thanmetallic devices thanks to its greater integration and simplicity of theload path, thus achieving the object specified above.

BRIEF DESCRIPTION OF THE FIGURES

Described below are certain aspects of the invention on the basis ofsome drawings forming an integral part of this specification, and inwhich

FIG. 1 is a schematic view in lateral elevation of the tail fuselage andof the empennage of an aircraft,

FIG. 2 is a schematic view in side elevation of an embodiment of thefitting with torsion box coupled to a motor/spindle unit;

FIG. 3 is a schematic view in front perspective, in partialcross-section, of the fitting with torsion box shown in FIG. 2;

FIG. 4 is a schematic view in cross-section along the line 4-4′ shown inFIG. 2;

FIG. 5 is a schematic view from the front, in partial cross-section, ofthe fitting with torsion box shown in FIG. 2.

Appearing in these figures are numerical references identifying thefollowing elements:

-   1 tail fuselage of the aircraft-   1 a horizontal stabilizer-   1 b vertical stabilizer-   1 c elevator-   1 d rudder-   1 e pivoting point of the horizontal stabilizer-   1 f fastening point of the horizontal stabilizer-   2 torsion box-   2 a first side wall-   2 b second side wall-   2 c stiffening holes-   3 a first means of attachment-   3 b second means of attachment-   4 stiffening element-   4 a first end part-   4 b second end part-   4 c central part-   4 d, 4 e first sections-   4 f, 4 g second sections-   4 h, 4 i third sections-   5 a, 5 b first primary passage holes-   5 c, 5 d second primary passage holes-   6 secondary passage hole-   7 a, 7 b first primary lugs-   7 c, 7 d second primary lugs-   8 additional laminated material-   9 spindle-   10 motor-   10 a fastening lug for motor-   10 b pin-   11 swivel-   11 a fastening lug for swivel-   11 b pin-   12 rivet

MODES OF EMBODIMENT OF THE INVENTION

FIG. 1 shows the tail fuselage 1 of a aircraft in which is arranged ahorizontal stabilizer 1 a, with its elevator 1 c, and also a verticalstabilizer 1 b with its rudder 1 d. The horizontal stabilizer 1 a istrimmable in a way that is conventional in itself by means of amotor/spindle mechanism connected to a fastening point 1 f, theactuation of which causes the stabilizer to pivot about the pivotingpoint 1 e, so that, in a way that is also conventional in itself, thehorizontal stabilizer 1 a, the elevator 1 c and the fastening point ifcan adopt the positions shown with the references 1 a′, 1 c′ and 1 a and1 c″, and 1 f′, 1 f″, respectively. Evidently, on the opposite side ofthe fuselage, not shown in FIG. 1, there is a right horizontalstabilizer with the elevator, analogous to the left horizontalstabilizer shown in FIG. 1.

FIGS. 2 to 5 show an embodiment of the invention in which the torsionbox 2 comprises a first side wall 2 a and first means of attachment 3 ain the form of brackets via which the first side wall 2 a can be rivetedto a first frame (not shown in the figures) of the tail fuselage of theaircraft, and a second side wall 2 b and second means of attachment 3 b,also in the form of brackets, via which the second side wall 2 b can beriveted to a second frame of the tail fuselage 1. The side walls 2 a, 2b of the torsion box 2 are attached together by means of a stiffeningelement 4 arranged between those side walls 2 a, 2 b. On each side ofthe stiffening element, each wall 2 a, 2 b presents individualstiffening holes intended to prevent buckling of those side walls 2 a, 2b. The stiffening element 4 comprises a first end part 4 a attached tothe first side wall 2 a of the torsion box, a second end part 4 battached to the second side wall 2 b of the torsion box, and a centralpart 4 c which joins those end parts 4 a, 4 b. The torsion box 2 and thestiffening element 4 are shaped from a plastic material reinforced withcarbon fiber.

Each end part 4 a, 4 b of the stiffening element 4 includes individualfirst sections 4 d, 4 e, which are extended in parallel to the sidewalls 2 a, 2 b to both sides of said central part 4 c, individual secondsections 4 f, 4 g which are respectively extended from one of the firstsections 4 d, 4 e to the corresponding side wall 2 a, 2 b, andindividual third sections 4 h, 4 i each one backing onto and attached tothe side wall 2 a, 2 b. It can be seen that the sections 4 d, 4 f, 4 hand 4 e, 4 g, 4 i which respectively shape the first end part 4 a andthe second end part 4 b of the stiffening element have a jointtransverse section in the form of an omega and on these sections 4 d, 4e, 4 f, 4 g, 4 h, 4 i of each end part 4 a, 4 b of the stiffeningelement 4 there is an additional laminated layer 8 arranged whichpresents a transverse section in the form of an omega similar to that ofthe said sections. This layer 8 can be obtained by means of anadditional laminate in such a way that it shapes a single piece with therest of the stiffening element 8. The respective third sections 4 h, 4 iand the corresponding parts of the additional laminated materialsrespectively arranged on these third sections are attached to thecorresponding side wall 2 a, 2 b by means of rivets 12. In turn, thecentral part 4 c of the stiffening element 8 comprises a reinforced zonewith two secondary passage holes 6 which shape the secondary fasteningfor the fitting.

The first sections 4 d of the first end part 4 a of the stiffeningelement 4 and the first sections 4 e of the second end part 4 b of thestiffening element 4 include individual first primary passage holes 5 a,5 b while the side walls 2 a, 2 b of the torsion box comprise individualsecond primary passage holes 5 c, 5 d. These primary passage holes 5 a,5 c, 5 b, 5 d are aligned and respectively located in the primary lugs 7a, 7 b, 7 c, 7 d emerging from the respective lower edges of the firstsections 4 d, 4 e of the stiffening element and from the respectivelower edges of the walls 2 a, 2 b in order to receive pin 10 b andcreate the primary fastening for complementary lugs 10 a of the motor 10which drives the spindle 9. The lugs 7 a, 7 b, 7 c, 7 d are reinforcedwith a hybrid titanium-CFRP laminate, conventional in itself.

1. Fitting with torsion box for coupling a motor/spindle unit fortrimming of a horizontal stabilizer of an aircraft, which comprises aduplicated primary fastening for the pivoting coupling of amotor/spindle unit, and a secondary fastening; wherein the torsion boxcomprises a first side wall and first means of attachment for attachingthe first side wall to a first frame of the tail fuselage of theaircraft, and a second side wall and second means of attachment forattaching the second side wall to a second frame of the tail fuselage;the side walls of the torsion box are attached together by a stiffeningelement arranged between those side walls; the stiffening elementcomprises a first end part attached to the first side wall, a second endpart attached to the second side wall and a central part which joinsthose end parts; each end part comprises individual first sections,which are extended in parallel to the side walls to both sides of saidcentral part, individual second sections which are respectively extendedfrom one of the first sections towards the corresponding side wall, andindividual third sections each one backing onto and attached to the sidewall; the first sections of the first end part of the stiffening elementand the first sections of the second end part of the stiffening elementinclude individual first primary passage holes and the side walls of thetorsion box comprise individual second primary passage holes, saidprimary passage holes being aligned in order to shape the primaryfastening; the secondary fastening is at least one secondary passagehole in the central wall of the stiffening element; the torsion box andthe stiffening element are shaped from plastic material reinforced withcarbon fiber.
 2. Fitting according to claim 1, wherein the first primarypassage holes are arranged in individual reinforced zones of the firstsections of the end parts of the stiffening element.
 3. Fittingaccording to claim 2, wherein the first primary passage holes arearranged in individual first primary lugs which emerge from respectiveedges of the first sections of the end parts of the stiffening element.4. Fitting according to claim 2, wherein the sections of each end partof the stiffening element include an additional laminated layer and inthat the first primary passage holes are arranged in individual firstprimary lugs which emerge from respective edges of the laminated layerin the first sections of the end parts of the stiffening element. 5.Fitting according to claim 2, wherein the second primary passage holesare arranged in individual reinforced zones of the side walls of thetorsion box.
 6. Fining according to claim 2, wherein the second primarypassage holes are arranged in individual second primary lugs whichemerge from respective edges of the side walls of the torsion box. 7.Fitting according to claim 2, wherein each secondary passage hole isarranged in a reinforced zone of the central part of the stiffeningelement.
 8. Fitting according to claim 2, wherein the third sections ofthe stiffening element are attached to the respective side wall of thetorsion box by means of gluing.
 9. Fitting according to claim 2, whereinthe third sections of the stiffening element are attached to therespective side wall of the torsion box by means of riveting. 10.Fitting according to claim 2, wherein the stiffening element and torsionbox are a monobloc piece.
 11. Fitting according to claim 1, wherein thefirst primary passage holes are arranged in individual first primarylugs which emerge from respective edges of the first sections of the endparts of the stiffening element.
 12. Fining according to claim 1,wherein the sections of each end part of the stiffening element includean additional laminated layer and in that the first primary passageholes are arranged in individual first primary lugs which emerge fromrespective edges of the laminated layer in the first sections of the endparts of the stiffening element.
 13. Fitting according to claim 12,wherein the additional laminated material is a layer attached to saidsections by lamination.
 14. Fitting according to claim 1, wherein thesecond primary passage holes are arranged in individual reinforced zonesof the side walls of the torsion box.
 15. Fitting according to claim 1,wherein the second primary passage holes are arranged in individualsecond primary lugs which emerge from respective edges of the side wallsof the torsion box.
 16. Fitting according to claim 1, wherein eachsecondary passage hole is arranged in a reinforced zone of the centralpart of the stiffening element.
 17. Fitting according to claim 1,wherein the third sections of the stiffening element are attached to therespective side wall of the torsion box by means of gluing.
 18. Fittingaccording to claim 1, wherein the third sections of the stiffeningelement are attached to the respective side wall of the torsion box bymeans of riveting.
 19. Fining according to claim 1, wherein thestiffening element and torsion box are a monobloc piece.